Bening and Moore are playing a couple who long ago used donated sperm to start a family. Years later, when their son and daughter (Hutcherson and Wasikowska) have grown up, they want to find the man behind the sperm. So, they hunt down Ruffalo's character, and he "totally upsets their family dynamic once he enters their lives."
This project is coming from Lisa Cholodenko, which bodes particularly well for the already-unique story. You might remember that she's the writer and director of Laurel Canyon, one of the few films to show the lovely Frances McDormand as a beautiful and carefree woman, rather than a quirky gal steeped in kitsch.
So, a filmmaker who can challenge the norm, a same-sex couple played by two multi-Oscar-nominated actresses, and an original storyline to boot? Pinch me, I must be dreaming. The film just started production, so I can only hope we get to see how this all pans out soon.